A president of the American Medical Jogger's Association, an affiliate of the American Medical Association, described the jogging experience this way: "I am convinced that jogging extends life." The National Jogging Association counts more than 10,000 dues paying members. The Roadrunners Club of America founded in 1957, now has more than 100 chapters across the country with 50,000 members.
From the proliferation of popular paperback books and specialized magazines, it is obvious that "jogging" as an exercise and a means to maintain one's health, is presently enjoying widespread popularity. Anyone doubting this conclusion need only pause a moment on a pleasant spring day in a park in any city, or walk along the roads in any suburb.
One reason for the popularity of jogging is the apparent ease with which it can be accomplished and the widespread consensus that there is great benefit to one's health with a minimum of danger from over exertion, if jogging is approached with some care, assuming that the jogger is in moderately good health. Of course, a physical examination should be made by competent medical practitioners before a program of jogging for health is attempted.
Although jogging has attained wide popular acceptance, there are medical and other personnel who regard jogging as less than beneficial. These people point out that jogging may be too strenuous an exercise for some people and, for the others, the trauma to the body caused by constant impact with hard surfaces normally found in city and surburban streets, can do serious damage to the human body. A list of common problems encountered by joggers or runners include: Achilles Pendinitis, Chrondromalacia of the knee, heel-bone damage, Leg and Foot bursitis, Shin Splints, leg-muscle pulls, back pain, muscle cramp, and twisted ankles.
The usual jogging style, as opposed to running and normal walking, normally results in the weight of the jogger landing on four or five square inches of the heel surface of the shoe. The impact force has been estimated at about three to four times the weight of the jogger. A jogger weighing 180 lbs. would therefor create a force of 720 lbs of shock on one heel. Considering the fact that each heel impacts the ground about 800 times per mile, it is easy to see why joggers can suffer from various ailments associated with impact which must be absorbed by the bones and muscles.
A number of different styles of jogging shoe have evolved in an attempt to absorb or mitigate the impact received by the jogger's heel, especially when a jogger is running on concrete or macadam surfaces normally encountered in urban and surburban jogging.
Sponge rubber material for use on the heel and sole of jogging shoes has been found generally inadequate in that it is too soft to provide adequate shock resistance. The harder materials such as nylon and high density rubber are too hard and transmit too much of the impact to the heel of the jogger. Often a combination of crepe and gum rubber are used in forming the sole of the joggers' shoe.
One popular style uses a crepe sole lined with a rubber bottom layer having pegs disposed downwardly from the harder rubber layer. Often the hard rubber layer curves around the back of the shoe to cover the rear of the heel. Other styles are more like sneakers, and, in fact, many people jog wearing just sneakers in spite of the probable inadequacy of most sneakers to absorb the tremendous impact to the heel, from jogging.
Although most prior art shoe designs have, to a greater or lesser extent, been able to mitigate the impact transmitted from the heel of the shoe to the heel of the jogger, they suffer from several potential related inadequacies.
The amount of shock absorption built into the heel of a jogging shoe is controlled by the available materials and the design of the manufacturer. As a result, a lighter weight person having large feet may have to use a shoe designed to absorb the shock of a much heavier person, while a heavy weight person having small feet will have the opposite problem, assuming that the manufacturer of the shoe has used some logical design means to build different shock absorbing characteristics into their shoes. In any case, there is generally no provision for adjustment for control of the amount of shock absorption obtainable in any particular shoe, although the same shoe may be used by joggers of greatly varying weights on surfaces varying from concrete to dirt or grass.
In order to create cushioning, support, and comfort presently the following devices are often inserted into existing jogging or running shoe:
heel lifts, heel cups, arch supports, inserts (custom made or molded supports); and insoles.